JP2012194300A - Electrophotographic toner, image forming device using the same, process cartridge, and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide electrophotographic toner in which charging stability and low temperature fixability are both achieved, and which is granulated in an aqueous medium.SOLUTION: The electrophotographic toner is granulated in the aqueous medium, and has a core-shell structure. The core includes a coloring agent and a binder resin. The shell has a first shell covering the whole of core surface and a second shell composed of resin fine particles fixed to the surface of the first shell. The resin constituting the first shell has a softening point of 90°C or higher and 120°C or lower. The resin constituting the second shell is a vinyl resin.

Description

  The present invention relates to an electrophotographic toner for developing an electrostatic latent image formed in electrophotography.

  In addition to the conventional kneading and pulverization method, the toner production method includes a suspension method and an emulsification method using an organic solvent and an aqueous solvent. There is known a production method called a chemical toner method such as a combination method, an aggregation method in which emulsified fine particles are produced and toner particles are aggregated to obtain toner particles, and even in the chemical toner, a resin that is advantageous for heat fixing on the toner core There is known a core-shell type toner in which the outside is covered in a granular form with a resin advantageous in chargeability and heat resistance.

Japanese Patent Application Laid-Open No. 2009-53501 of Patent Document 1 describes a capsule toner in which a surface layer is formed on the surface of toner base particles that are excellent in heat-resistant storage stability and low-temperature fixability.
In this toner, the pigment is unevenly distributed on the surface of the core, and it is difficult to maintain the charging performance through environmental fluctuations simply by forming a shell layer.

Japanese Patent Application Laid-Open No. 2005-099233 of Patent Document 2 discloses a toner in which two layers of shells are formed so as not to expose a pigment and a release agent, and variation in charge amount due to environmental variation is suppressed. .
However, when forming the shell layer, it is necessary to heat and fuse with the core for a long time. The fine particles forming the shell are buried in the core with a low softening temperature, and the shell is easily damaged. The film thickness of the layer was increased, and the low temperature fixability of the core could not be fully utilized, making it difficult to achieve both charging stability and low temperature fixability.

An object of the present invention is to provide an electrophotographic toner that is granulated in an aqueous medium having both charge stability and low-temperature fixability.

The above problem is solved by completely covering the entire core surface with a first shell having a softening point of 90 ° C. or higher and 120 ° C. or lower, and fixing the vinyl resin particles to the first shell surface.
That is, as a result of intensive studies, the present inventors have formed the first shell with a resin having a high affinity for the core, so that the core surface is completely covered without heating for a long time, and the first shell It has been found that both the charging stability and the low-temperature fixability can be achieved by fixing the vinyl resin particles on the shell.

The said subject is solved by following (1)-(11) of this invention.
(1) An electrophotographic toner granulated in an aqueous medium, wherein the toner has a core-shell structure, the core includes a colorant and a binder resin, and the shell covers the entire core surface. The first shell and the second shell made of resin fine particles fixed to the surface of the first shell, and the resin constituting the first shell has a softening point of 90 ° C. or higher and 120 ° C. or lower, The electrophotographic toner, wherein the resin constituting the second shell is a vinyl resin.
(2) The toner for electrophotography as described in (1) above, wherein the coverage of the first shell with the second shell is 30% or more and 80% or less.
(3) The toner according to (1) or (2) above, wherein an average diameter of an exposed portion of the vinyl resin particles of the second shell is 150 nm or more and 400 nm or less.
(4) The electrophotographic photograph as described in any one of (1) to (3) above, wherein the vinyl resin fine particles contain 80% by mass or more of a portion derived from an aromatic compound having a vinyl polymerizable functional group. Toner.
(5) The electrophotographic toner according to any one of (1) to (4), wherein the binder resin of the core is a polyester resin.
(6) The electrophotographic toner according to any one of (1) to (5), wherein the resin constituting the first shell is a polyester resin.
(7) The toner for electrophotography according to any one of (1) to (6), wherein the toner is magenta toner or yellow toner.
(8) A developer containing the electrophotographic toner according to any one of (1) to (7).
(9) A process cartridge which integrally supports the latent image carrier, the developing means, the charging means and / or the cleaning means, and is detachable from the main body of the image forming apparatus, the developing means Is a process cartridge which holds the developer according to (8).
(10) a charging step for uniformly charging the surface of the latent image carrier,
An exposure process for exposing the surface of the charged latent image carrier based on the image data and writing an electrostatic latent image;
A developer layer having a predetermined layer thickness is formed on the developer carrier by a developer layer regulating member, and the electrostatic latent image formed on the surface of the latent image carrier is developed through the developer layer to be visualized. A development process to
A transfer step of transferring a visible image on the surface of the latent image carrier to the transfer target;
A fixing step of fixing a visible image on the transfer target,
An image forming method using the developer described in (8) above as a developer.
(11) A latent image carrier that carries a latent image, a charging unit that uniformly charges the surface of the latent image carrier, and the surface of the latent image carrier that has been charged is exposed based on image data. An exposure unit for writing an image, a developing unit for supplying toner to the electrostatic latent image formed on the surface of the latent image carrier to make it visible, and a visible image on the surface of the latent image carrier are transferred to the transfer target An image forming apparatus comprising: a transfer unit; and a fixing unit that fixes a visible image on a transfer target, wherein the developing unit holds the developer described in (8). Forming equipment.

As will be understood from the following detailed and specific description, according to the present invention, an electrophotographic toner having both charging stability and low-temperature fixability can be provided.

FIG. 3 is an explanatory diagram illustrating a main part of an embodiment of an image forming apparatus in which the electrophotographic toner of the present invention is used. FIG. 3 is an explanatory diagram illustrating a configuration of a fixing device used in an image forming apparatus in which the electrophotographic toner of the present invention is used. FIG. 6 is an explanatory diagram illustrating another example of an image forming apparatus in which the electrophotographic toner of the present invention is used. FIG. 6 is an explanatory diagram illustrating another example of an image forming apparatus in which the electrophotographic toner of the present invention is used. FIG. 3 is an explanatory diagram showing a process cartridge in which the electrophotographic toner of the present invention is used.

The electrophotographic toner of the present invention will be described in detail.
<Toner particles>
The toner of the present invention is an electrophotographic toner granulated in an aqueous medium, the toner has a core-shell structure, the core includes a colorant and a binder resin, and the shell has a core surface. It is composed of a first shell covering the whole and a second shell made of resin particles fixed to the surface of the first shell, and the resin constituting the first shell has a softening point of 90 ° C. or higher and 120 ° C. or lower. The toner constituting the second shell is a vinyl resin, and may contain an external additive, a charge control agent, and the like.

The toner of the present invention has a first shell and a second shell formed thereon.
(First shell)
The first shell completely covers the core surface, prevents the influence of the pigment and wax in the core on the chargeability, and improves the low-temperature fixability.
As long as the resin constituting the first shell is a resin having a softening point of 90 to 120 ° C., a known resin that has been conventionally used in toners can be used, but those having a polyester skeleton are preferable, From the viewpoint of adhesiveness to the core, it is preferable to have an affinity for the binder resin in the core.
When the softening point is less than 90 ° C, the blocking resistance is lowered, and when it exceeds 120 ° C, the low-temperature fixability is lowered.
In the present invention, since the second shell is formed, the softening point of the first shell can be lowered and the low-temperature fixability can be improved.

The first shell can be formed by adding a resin fine particle dispersion containing fine particles of the resin to an aqueous medium containing oil droplets (core particles) and attaching the resin fine particles to the oil droplets.
The volume average particle diameter of the resin fine particles is preferably 100 to 150 nm. If it is less than 100 nm, it is easy to aggregate and difficult to produce, and if it is more than 150 nm, the shell layer is thick and the wax is difficult to exude.

The temperature at which the resin fine particles adhere to the core particles is 10 to 45 ° C, preferably 20 to 30 ° C. If the temperature exceeds 45 ° C., the energy required for production increases, which not only increases the environmental impact of the production, but also makes it easier for resin fine particles to enter the core particles (core), making it difficult to completely cover the core surface. Become.
On the other hand, when the temperature is less than 10 ° C., the viscosity of the dispersion increases, and the resin particles may not adhere sufficiently.
In addition, the toner particle matrix and the resin particles may be mixed and stirred, and mechanically adhered and coated.

(Second shell)
The second shell is obtained by fixing vinyl resin fine particles on the first shell with a gap, and has a blocking resistance by a spacer function, and does not hinder the fixing property of the core particles and the first shell. .

The coverage of the first shell with the second shell is preferably 30% or more and 80% or less. If it is less than 30%, the charge stability and blocking resistance may be inferior, and if it exceeds 80%, the low-temperature fixability of the core and the first shell may not be fully utilized.

The vinyl resin preferably has a structure that is easily charged, and the styrene monomer has an aromatic ring structure having an electron orbit in which electrons can stably exist. Therefore, the vinyl resin fine particles used in the present invention Is preferably obtained by polymerizing a monomer mixture containing at least a styrene monomer.
The content of the styrenic monomer in the monomer mixture is 50 to 100% by weight, preferably 80 to 100% by weight. When the styrene monomer is less than 50% by weight, the chargeability of the obtained toner particles becomes poor.

Here, the styrene monomer refers to an aromatic compound having a vinyl polymerizable functional group. Examples of the polymerizable functional group include a vinyl group, an isopropenyl group, an allyl group, an acryloyl group, and a methacryloyl group.
Specific examples of the styrene monomer include styrene, α-methylstyrene, 4-methylstyrene, 4-ethylstyrene, 4-tert-butylstyrene, 4-methoxystyrene, 4-ethoxystyrene, 4-carboxystyrene, and metal salts thereof. , 4-styrenesulfonic acid or a metal salt thereof, 1-vinylnaphthalene, 2-vinylnaphthalene, allylbenzene, phenoxyalkylene glycol acrylate, phenoxyalkylene glycol methacrylate, phenoxy polyalkylene glycol acrylate, phenoxy polyalkylene glycol methacrylate, and the like. It is preferable to use mainly styrene which is easily available and has excellent reactivity and high chargeability.

  In the vinyl resin used in the present invention, the acid monomer may be used in an amount of 0 to 7% by weight, preferably 0 to 4% by weight of the monomer mixture, and more preferably no acid monomer is used. . When the acid monomer is used in an amount exceeding 7% by weight, the resulting vinyl resin fine particles have high dispersion stability, so that such a vinyl resin is contained in a dispersion in which oil droplets are dispersed in an aqueous phase. Even if resin fine particles are added, they are difficult to adhere at room temperature or are easily detached even if they are attached, and they are easily removed in the process of solvent removal, washing, drying, and external addition treatment. Furthermore, when the amount of the acid monomer used is 4% by weight or less, the change in chargeability can be reduced depending on the environment in which the obtained toner particles are used.

Here, the acid monomer means a compound having a vinyl polymerizable functional group and an acid group, and examples of the acid group include carboxylic acid, sulfonyl acid, and phosphonic acid.
Examples of the acid monomer include carboxyl group-containing vinyl monomers and salts thereof ((meth) acrylic acid, (anhydrous) maleic acid, monoalkyl maleate, fumaric acid, monoalkyl fumarate, crotonic acid, itaconic acid, itaconic acid mono Alkyl, itaconic acid glycol monoether, citraconic acid, monoalkyl citraconic acid, cinnamic acid, etc.), sulfonic acid group-containing vinyl monomers, vinyl sulfate monoesters and salts thereof, phosphate group-containing vinyl monomers and salts thereof, etc. There is. Of these, (meth) acrylic acid, (anhydrous) maleic acid, monoalkyl maleate, fumaric acid, and monoalkyl fumarate are preferred.

Although it does not specifically limit as a method of obtaining vinyl resin fine particles, The following (a)-(f) is mentioned.
(A) The monomer mixture is reacted by a polymerization reaction such as a suspension polymerization method, an emulsion polymerization method, a seed polymerization method or a dispersion polymerization method to produce a dispersion of vinyl resin fine particles.
(B) The monomer mixture is polymerized in advance, and the resin obtained is pulverized using a mechanical pulverizer or jet pulverizer and then classified to produce resin fine particles.
(C) Resin fine particles are produced by polymerizing the monomer mixture in advance and spraying the resulting resin solution in a solvent in the form of a mist.
(D) polymerizing the monomer mixture in advance, adding a solvent to the resin solution obtained by dissolving the obtained resin in a solvent, or cooling the resin solution previously dissolved in a solvent to precipitate resin fine particles; The solvent is removed to produce resin fine particles.
(E) A monomer solution is polymerized in advance, and a resin solution obtained by dissolving the obtained resin in a solvent is dispersed in an aqueous medium in the presence of an appropriate dispersant, and the solvent is removed by heating or decompression.
(F) A monomer mixture is polymerized in advance, an appropriate emulsifier is dissolved in a resin solution obtained by dissolving the obtained resin in a solvent, and water is added to perform phase inversion emulsification.
Among them, the method (a) is preferable because it is easy to produce and the resin fine particles can be obtained as a dispersion, and can be smoothly applied to the next step.

In the method (a), when the polymerization reaction is performed, a dispersion stabilizer is added to the aqueous medium, or the dispersion stability of the resin fine particles obtained by polymerization can be imparted to the monomer that performs the polymerization reaction. It is preferable to add a stable monomer (so-called reactive emulsifier) or to use these two means in combination to impart dispersion stability of the resulting vinyl resin fine particles. If a dispersion stabilizer or reactive emulsifier is not used, the dispersion state of the particles cannot be maintained, so the vinyl resin cannot be obtained as fine particles, or the dispersion stability of the obtained resin fine particles is low, so that the storage stability The toner particles are agglomerated during storage, or the dispersion stability of the particles in the resin fine particle adhesion process described later is reduced, so that the core particles easily aggregate and coalesce and the toner particles finally obtained This is not preferable because the uniformity of the particle size, shape, surface, and the like deteriorates.

Examples of the dispersion stabilizer include surfactants and inorganic dispersants. Examples of the surfactant include anionic surfactants such as alkylbenzene sulfonates, α-olefin sulfonates, phosphate esters, and alkylamines. Amine salts such as salts, amino alcohol fatty acid derivatives, polyamine fatty acid derivatives, imidazoline, alkyltrimethylammonium salts, dialkyldimethylammonium salts, alkyldimethylbenzylammonium salts, pyridinium salts, alkylisoquinolinium salts, benzethonium chloride, etc. Nonionic surfactants such as quaternary ammonium salt type cationic surfactants, fatty acid amide derivatives, polyhydric alcohol derivatives, such as alanine, dodecyldi (aminoethyl) glycine, di (octylaminoethyl) glycine and N-alkyl N, amphoteric surfactants such as N- dimethyl ammonium betaine and the like. As the inorganic dispersant, tricalcium phosphate, calcium carbonate, titanium oxide, colloidal silica, hydroxyapatite and the like are used.

The weight average molecular weight of the vinyl resin is 3000 to 300000, preferably 4000 to 100000, more preferably 5000 to 50000. If the weight average molecular weight is less than 3000, the mechanical strength of the vinyl resin is weak and fragile, and the surface of the colored resin particles easily changes depending on the use situation depending on the application of the colored resin particles finally obtained. For example, it is not preferable because it causes a significant change in chargeability, contamination such as adhesion to peripheral agents, and the occurrence of quality problems associated therewith. On the other hand, when the molecular weight exceeds 300,000, the molecular ends are decreased, so that the entanglement of the molecular chain with the core particle is decreased, and the adhesion to the core particle is decreased.

Further, the diameter of the exposed portion of the resin particles of the second shell fixed to the first shell is preferably 50 to 800 nm on average, and more preferably 150 to 400 nm. Within the above range, the chargeability can be improved and the resin fine particles can be prevented from being detached.
The average diameter of the exposed portions of the resin particles constituting the second shell on the toner surface can be controlled by the particle size and composition of the vinyl resin fine particles as a raw material. For example, if the particle diameter of the vinyl resin fine particles is reduced, the average diameter of the exposed portions of the resin particles constituting the second shell on the toner surface is reduced.
In order to reduce the particle size of the vinyl resin fine particles, the amount of the surfactant may be increased. In addition, when a polar substance such as methyl methacrylate is added to the vinyl fine particles, the average diameter of the exposed portions of the resin particles constituting the second shell on the toner surface increases.

(Core particle)
The core particle is obtained by granulation in an aqueous medium.
Granulation methods in aqueous media include suspension and emulsification methods using organic solvents and aqueous media, suspension polymerization methods in which polymerized monomer droplets are controlled to obtain toner particles directly, and emulsified fine particles are produced. There is a production method called a so-called wet granulation or chemical toner method such as an agglomeration method for agglomerating them to obtain toner particles, and any of them can be used in the present invention.

Hereinafter, the dissolution suspension method will be described as an example.
(Dissolution suspension method)
As a method for producing a toner using the dissolution suspension method, at least a solution or dispersion obtained by dissolving or dispersing a toner composition comprising a resin and a colorant in an organic solvent is used. A method of obtaining a toner slurry by dispersing the organic solvent in an aqueous solvent using an ordinary stirrer, homomixer, homogenizer, etc. so as to obtain a toner having a desired particle size distribution, and then removing the organic solvent. Can be mentioned. The toner can be isolated by collecting and drying by washing and filtration according to a known method.

(About the resin used)
In the dissolution suspension method, any resin that can be dissolved in a solvent can be used in production.
Specific examples include resins conventionally used in toners, including polyester resins, styrene-acrylic resins, polyol resins, vinyl resins, polyurethane resins, epoxy resins, polyamide resins, polyimide resins, silicon resins, phenols. There are resin, melamine resin, urea resin, aniline resin, ionomer resin, polycarbonate resin and the like. From the viewpoint of fixing properties, a polyester resin is preferably used.

(Polyester resin)
Examples of the polyester resin include a polycondensate of polyol (1) and polycarboxylic acid (2).

(Polyol)
Examples of the polyol (1) include a diol (1-1) and a tri- or higher valent polyol (1-2), (1-1) alone or (1-1) and a small amount of (1-2). Mixtures are preferred. Diol (1-1) includes alkylene glycol (ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, etc.); alkylene ether glycol (diethylene glycol) , Triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, etc.); alicyclic diols (1,4-cyclohexanedimethanol, hydrogenated bisphenol A, etc.); bisphenols (bisphenol A, bisphenol) F, bisphenol S, etc.); alkylene oxide (ethylene oxide, propylene oxide, butylene oxide, etc.) adduct of the above alicyclic diol; Alkylene oxide phenol compound (ethylene oxide, propylene oxide, butylene oxide, etc.), etc. adducts.
Among these, preferred are alkylene glycols having 2 to 12 carbon atoms and alkylene oxide adducts of bisphenols, and particularly preferred are alkylene oxide adducts of bisphenols and alkylene glycols having 2 to 12 carbon atoms. It is a combined use.
The trihydric or higher polyol (1-2) includes 3 to 8 or higher polyhydric aliphatic alcohols (glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, sorbitol, etc.); trihydric or higher phenols (Trisphenol PA, phenol novolak, cresol novolak, etc.); and alkylene oxide adducts of the above trivalent or higher polyphenols.

(Polycarboxylic acid)
Examples of polycarboxylic acid (2) include dicarboxylic acid (2-1) and trivalent or higher polycarboxylic acid (2-2). (2-1) alone or (2-1) and a small amount of ( The mixture of 2-2) is preferred.
Dicarboxylic acid (2-1) includes alkylene dicarboxylic acid (succinic acid, adipic acid, sebacic acid, etc.); alkenylene dicarboxylic acid (maleic acid, fumaric acid, etc.); aromatic dicarboxylic acid (phthalic acid, isophthalic acid, terephthalic acid) And naphthalenedicarboxylic acid). Of these, preferred are alkenylene dicarboxylic acids having 4 to 20 carbon atoms and aromatic dicarboxylic acids having 8 to 20 carbon atoms.
Examples of the trivalent or higher polycarboxylic acid (2-2) include aromatic polycarboxylic acids having 9 to 20 carbon atoms (trimellitic acid, pyromellitic acid, and the like). In addition, as polycarboxylic acid (2), you may make it react with polyol (1) using the acid anhydride or lower alkyl ester (methyl ester, ethyl ester, isopropyl ester, etc.) of the above-mentioned thing.

(Ratio of polyol and polycarboxylic acid)
The ratio of the polyol (1) to the polycarboxylic acid (2) is usually 2/1 to 1/1, preferably 1. as the equivalent ratio [OH] / [COOH] of the hydroxyl group [OH] and the carboxyl group [COOH]. 5/1 to 1/1, more preferably 1.3 / 1 to 1.02 / 1.

(Organic solvent)
An organic solvent having a boiling point of less than 100 ° C. is preferably used so that it can be easily removed. Such organic solvents include toluene, xylene, benzene, carbon tetrachloride, methylene chloride, 1,2-dichloroethane, 1,1,2-trichloroethane, trichloroethylene, chloroform, monochlorobenzene, dichloroethylidene, methyl acetate, ethyl acetate. , Methyl ethyl ketone, methyl isobutyl ketone and the like, and may be used alone or in combination of two or more.

(Aqueous medium)
The aqueous solvent may be water alone, but a solvent miscible with water may be used in combination. Examples of the miscible solvent include alcohols such as methanol, isopropanol and ethylene glycol, cellosolves such as dimethylformamide, tetrahydrofuran and methyl cellosolve, and lower ketones such as acetone and methyl ethyl ketone. The amount of the aqueous solvent used relative to 100 parts by mass of the toner material is usually 50 to 2000 parts by mass, preferably 100 to 1000 parts by mass. If the amount of the aqueous solvent used is less than 50 parts by mass, the dispersion state of the toner material may be deteriorated. Moreover, when it exceeds 2000 mass parts, it is not economical.

(Inorganic dispersant)
Inorganic dispersants include tricalcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate, bentonite, Alumina, calcium carbonate, titanium oxide, colloidal silica, hydroxyapatite, and the like can be used.

(wax)
As the wax used in the present invention, known waxes can be used, for example, polyolefin wax (polyethylene wax, polypropylene wax, etc.); long chain hydrocarbon (paraffin wax, Fischer-Tropsch wax, sazol wax, etc.); carbonyl group-containing wax Etc. Carbonyl group-containing waxes include polyalkanoic acid esters (carnauba wax, montan wax, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1, 18-octadecanediol distearate etc.); polyalkanol esters (tristearyl trimellitic acid, distearyl maleate etc.); polyalkanoic acid amides (ethylenediamine dibehenyl amide etc.); polyalkylamides (trimellitic acid tristearyl amide etc.) ); And dialkyl ketones (such as distearyl ketone). Of these, polyolefin waxes and long-chain hydrocarbons are preferred because of their low polarity and low melt viscosity, and paraffin wax and Fischer-Tropsch wax are particularly preferred.

(Coloring agent)
In the toner of the present invention, a known colorant conventionally used in full color toners may be used. For example, carbon black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, copper phthalocyanine, malachite green oxalate, lamp black, rose bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 184, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Solvent Yellow 162, C.I. I. Pigment yellow 180, C.I. I. Pigment yellow 185, C.I. I. Pigment blue 15: 1, C.I. I. And CI Pigment Blue 15: 3.
When a pigment having an NH structure portion, such as a magenta or yellow pigment, is produced in an aqueous medium, it often exists near the boundary between the aqueous medium and the oil phase due to the characteristics of the structure.
Since the present invention covers the entire core surface containing the colorant, there is no fluctuation in the toner charge amount due to environmental fluctuations even when an NH structure portion such as magenta or yellow pigment is used. Therefore, it is particularly useful when a magenta or yellow pigment is used.

The content of the colorant in the toner particles is preferably in the range of 2 to 15 parts by weight with respect to 100 parts by weight of the total binder resin. It is preferable from the viewpoint of dispersibility that the colorant is used in the form of a masterbatch dispersed in a mixed binder resin of the first binder resin and the second binder resin used. The addition amount of the masterbatch may be an amount such that the amount of the colorant contained is within the above range. The colorant content in the masterbatch is preferably 20 to 40% by weight.

<Manufacturing method>
Next, the manufacturing process will be described.
(Oil phase creation process)
As a method for preparing an oil phase in which a resin, a colorant or the like is dissolved or dispersed in an organic solvent, the resin, the colorant or the like is gradually added to the organic solvent while stirring to dissolve or disperse. That's fine. However, when using a pigment as a colorant or adding a wax or charge control agent that is difficult to dissolve in an organic solvent, the particles may be made smaller prior to addition to the organic solvent. Good.
Further, as another means, if a thing that melts below the boiling point of the organic solvent is dispersed, in the organic solvent, if necessary, a dispersion aid is added and heated with stirring with the dispersoid, Once dissolved, the mixture may be cooled with stirring or shearing to crystallize to produce dispersoid microcrystals.
The colorant, wax, and charge control agent dispersed using the above means may be further dispersed after being dissolved or dispersed together with the resin in an organic solvent. For dispersion, a known disperser such as a bead mill or a disk mill can be used.

(Core particle production process)
There is no particular limitation on the method for preparing a core particle dispersion in which the oil phase obtained in the above-described step is dispersed in an aqueous medium having at least a surfactant and core particles made of the oil phase are dispersed. However, known equipment such as a low-speed shearing type, a high-speed shearing type, a friction type, a high-pressure jet type, and an ultrasonic wave can be applied.
In order to make the particle size of the dispersion 2 to 20 μm, a high-speed shearing type is preferable. When a high-speed shearing disperser is used, the rotational speed is not particularly limited, but is usually 1000 to 30000 rpm, preferably 5000 to 20000 rpm. The dispersion time is not particularly limited, but in the case of a batch method, it is usually 0.1 to 5 minutes. If the dispersion is performed for more than 5 minutes, particles having an undesirably small diameter may remain, or the dispersion may be overdispersed, resulting in instability of the system and generation of aggregates and coarse particles. It is not preferable.
As temperature at the time of dispersion | distribution, it is 0-40 degreeC normally, Preferably it is 10-30 degreeC. If it exceeds 40 ° C., the molecular motion becomes active, so that the dispersion stability is lowered and aggregates and coarse particles are easily generated, which is not preferable. On the other hand, when the temperature is less than 0 ° C., the viscosity of the dispersion increases, and the shear energy required for dispersion increases, so that the production efficiency decreases.
As the surfactant, the same surfactant as described in the explanation of the method for producing fine resin particles can be used. However, in order to efficiently disperse oil droplets containing a solvent, a disulfonate having a high HLB is used. preferable. The surfactant may have a concentration in the aqueous medium of 1 to 10% by weight, preferably 2 to 8% by weight, more preferably 3 to 7% by weight. If it exceeds 10% by weight, the oil droplets will be too small, or a reverse micelle structure will be formed and the dispersion stability will be lowered, resulting in the coarsening of the oil droplets. On the other hand, if it is less than 1% by weight, the oil droplets cannot be stably dispersed and the oil droplets become coarse, which is not preferable.

(Core-shell structure forming process)
The obtained core particle dispersion can keep the core particle droplets stably while stirring.
In this state, the resin fine particle dispersion used as the first shell is charged, and then the vinyl resin fine particle dispersion is charged to adhere onto the core particles.
The introduction of each resin fine particle dispersion is preferably performed over 30 seconds. If the charging is performed in less than 30 seconds, it is not preferable because the dispersion system is rapidly changed and aggregated particles are generated or the resin fine particles are not uniformly adhered. On the other hand, it is not preferable from the viewpoint of production efficiency to add to the dark cloud for a long time, for example, exceeding 60 minutes.
The resin fine particle dispersion may be diluted or concentrated to adjust the concentration as appropriate before being added to the core particle dispersion. The concentration of the resin fine particle dispersion is preferably 5 to 30% by mass, and more preferably 8 to 20% by mass. If it is less than 5%, the change in the concentration of the organic solvent accompanying the introduction of the dispersion is large, and the adhesion of the resin fine particles becomes insufficient. Further, if it exceeds 30% by mass, the resin fine particles are likely to be unevenly distributed in the core particle dispersion, and as a result, the adhesion of the resin fine particles becomes excessive. The coverage of the second shell layer with respect to the core particles coated with the first shell layer is preferably 30 to 80%, and the coverage is the above-described concentration adjustment and the amount of vinyl resin added when vinyl fine particles are added. Can be controlled by.

Resin fine particles adhere to the core particles with sufficient strength because the affinity between the resin fine particles and the core particles is high, and when the resin fine particles adhere to the core particle droplets, the core particles are freely deformed. This is probably because the resin fine particle interface and the contact surface are sufficiently formed, and the resin fine particles are swollen or dissolved by the organic solvent, and the resin fine particles and the resin in the core particles are likely to adhere to each other. It is.
Therefore, in this state, the organic solvent needs to be sufficiently present in the system. Specifically, in the state of the core particle dispersion, it is 50% by mass to 150% by mass, preferably 70% by mass with respect to the solid content (resin, colorant, and if necessary, release agent, charge control agent, etc.). It may be in the range of% to 125% by mass. If it exceeds 150% by mass, the amount of colored resin particles obtained in a single production process is reduced and the production efficiency is low, and if there is a large amount of organic solvent, the dispersion stability is lowered and stable production becomes difficult. .

Whether or not the first shell layer is formed can be confirmed by STEM observation of the cross section of the toner, and whether or not the second shell layer is formed can be confirmed by performing SEM observation.

<Demelting process>
In order to remove the organic solvent from the obtained colored resin dispersion, it is possible to employ a method in which the entire system is gradually heated while being stirred to completely evaporate and remove the organic solvent in the droplets.
Alternatively, the obtained colored resin dispersion can be sprayed into a dry atmosphere while stirring to completely remove the organic solvent in the droplets. Alternatively, the colored resin dispersion may be decompressed while stirring to evaporate and remove the organic solvent. The latter two means can be used in combination with the first means.
As a dry atmosphere in which the emulsified dispersion is sprayed, a gas obtained by heating air, nitrogen, carbon dioxide gas, combustion gas, or the like, in particular, various air currents heated to a temperature equal to or higher than the boiling point of the highest boiling solvent used is generally used. Sufficient quality can be obtained with a short treatment such as spray dryer, belt dryer or rotary kiln.

<Aging process>
When a modified resin having an isocyanate group at the terminal is added, an aging step may be performed in order to advance the elongation / crosslinking reaction of the isocyanate. The aging time is usually 10 minutes to 40 hours, preferably 2 to 24 hours. The reaction temperature is usually 0 to 65 ° C, preferably 35 to 50 ° C.

<Washing process>
The dispersion of the colored resin particles obtained by the above method contains secondary materials such as surfactants and other dispersants in addition to the colored resin particles. I do. Methods for washing the colored resin particles include methods such as a centrifugal separation method, a vacuum filtration method, and a filter press method, but are not particularly limited in the present invention. Either method can give a cake of colored resin particles, but if it cannot be washed sufficiently by a single operation, the obtained cake is again dispersed in an aqueous solvent to form a slurry and colored by any of the above methods. The step of taking out the resin particles may be repeated, and if washing is performed by a vacuum filtration method or a filter press method, an aqueous solvent is passed through the cake and a method of washing away the secondary material that the colored resin particles have embraced is adopted. Also good. As the aqueous solvent used for this washing, water or a mixed solvent obtained by mixing water and alcohol such as methanol or ethanol is used, but water is preferably used in view of cost and environmental load due to wastewater treatment.

<Drying process>
Since the washed colored resin particles contain a large amount of the aqueous medium, only the colored resin particles can be obtained by drying and removing the aqueous medium. Drying methods such as spray dryers, vacuum freeze dryers, vacuum dryers, stationary shelf dryers, mobile shelf dryers, fluidized tank dryers, rotary dryers, and agitation dryers are used as drying methods. be able to. The dried colored resin particles are preferably dried until the water content finally becomes less than 1%. If the colored resin particles after drying are softly agglomerated and inconvenience occurs during use, use a device such as a jet mill, a Henschel mixer, a super mixer, a coffee mill, an auster blender, or a food processor. It may be crushed to loosen the soft agglomeration.

<External processing>
The obtained dried toner powder is mixed with different kinds of particles such as charge control fine particles and fluidizer fine particles, or fixed and fused on the surface by applying mechanical impact force to the mixed powder. It is possible to prevent the dissociation of the foreign particles from the surface of the composite particle to be formed. Specific means include a method of applying an impact force to the mixture by blades rotating at high speed, a method of injecting and accelerating the mixture in a high-speed air stream, and causing particles or composite particles to collide with an appropriate collision plate, etc. is there. As equipment, Ong mill (manufactured by Hosokawa Micron Co., Ltd.), I-type mill (manufactured by Nippon Pneumatic Co., Ltd.) has been modified to lower the pulverization air pressure, hybridization system (manufactured by Nara Machinery Co., Ltd.), kryptron System (manufactured by Kawasaki Heavy Industries, Ltd.), automatic mortar, etc.

[Image Forming Method, Image Forming Apparatus, Process Cartridge]
<Image forming apparatus, process cartridge>
The image forming apparatus of the present invention forms an image using the toner of the present invention. The toner of the present invention can be used as either a one-component developer or a two-component developer, but is preferably used as a one-component developer. The image forming apparatus of the present invention preferably has an endless intermediate transfer unit. Furthermore, the image forming apparatus of the present invention preferably includes a photosensitive member and a cleaning unit that cleans the toner remaining on the photosensitive member and / or the intermediate transfer unit. At this time, the cleaning means may or may not have a cleaning blade. The image forming apparatus of the present invention preferably includes a fixing unit that fixes an image using a roller having a heating device or a belt having a heating device. Further, the image forming apparatus of the present invention preferably has a fixing unit that does not require oil application to the fixing member. Furthermore, it is preferable to include other means appropriately selected as necessary, for example, static elimination means, recycling means, control means, and the like.

  In the image forming apparatus of the present invention, the photosensitive member and the constituent elements such as the developing unit and the cleaning unit may be configured as a process cartridge, and the process cartridge may be configured to be detachable from the main body of the image forming apparatus. Further, at least one of a charging unit, an exposure unit, a developing unit, a transfer unit, a separating unit, and a cleaning unit is supported together with a photosensitive member to form a process cartridge, and a single unit that is detachable from the image forming apparatus main body. It is good also as a structure which can be attached or detached using guide means, such as a rail of a forming apparatus main body.

  FIG. 1 shows an example of an image forming apparatus of the present invention. In this image forming apparatus, a latent image carrier (1) that is driven to rotate in the clockwise direction in FIG. 1 is housed in a main body housing (not shown), and around the latent image carrier (1). In addition, a charging device (2), an exposure device (3), a developing device (4) having the electrostatic image developing toner (T) of the present invention, a cleaning unit (5), an intermediate transfer member (6), a support roller ( 7), a transfer roller (8), a charge eliminating means (not shown), and the like.

  The image forming apparatus includes a paper feed cassette (not shown) that stores a plurality of recording papers (P) as an example of a recording medium, and the recording paper (P) in the paper feed cassette is a paper feed (not shown). After the timing is adjusted by a pair of registration rollers (not shown) one by one by a roller, the sheet is fed between a transfer roller (8) as a transfer means and an intermediate transfer body (6).

  In this image forming apparatus, the latent image carrier (1) is rotated clockwise in FIG. 1 to uniformly charge the latent image carrier (1) with the charging device (2), and then the exposure device ( 3) to irradiate the laser modulated with the image data to form an electrostatic latent image on the latent image carrier (1), and to the developing device (4) on the latent image carrier (1) on which the electrostatic latent image is formed. ) To attach toner and develop. Next, a transfer bias is applied from the latent image carrier (1) on which the toner image is formed by the developing device (4) to the intermediate transfer member (6) to transfer the toner image onto the intermediate transfer member (6). By transferring the recording paper (P) between the intermediate transfer body (6) and the transfer roller (8), the toner image is transferred to the recording paper (P). Further, the recording paper (P) on which the toner image is transferred is conveyed to a fixing means (not shown).

  The fixing unit includes a fixing roller heated to a predetermined fixing temperature by a built-in heater and a pressure roller pressed against the fixing roller with a predetermined pressure, and heats the recording paper conveyed from the transfer roller (8). After pressurizing and fixing the toner image on the recording paper on the recording paper, it is discharged onto a paper discharge tray (not shown).

  On the other hand, the image forming apparatus further rotates the latent image carrier (1) on which the toner image is transferred onto the recording paper by the transfer roller (8), and the cleaning unit (5) applies the surface to the surface of the latent image carrier (1). After the remaining toner is scraped off and removed, the charge is removed by a charge removal device (not shown). The image forming apparatus uniformly charges the latent image carrier (1) neutralized by the static eliminator with the charging device (2), and then performs the next image formation in the same manner as described above.

Hereinafter, each member suitably used for the image forming apparatus of the present invention will be described in detail.
The material, shape, structure, size and the like of the latent image carrier (1) are not particularly limited and may be appropriately selected from known ones. The shape may be a drum shape or a belt shape. Examples of the material include inorganic photoreceptors such as amorphous silicon and selenium, and organic photoreceptors such as polysilane and phthalopolymethine. Among these, amorphous silicon and organic photoreceptors are preferable from the viewpoint of long life.

  The electrostatic latent image can be formed on the latent image carrier (1) by, for example, charging the surface of the latent image carrier (1) and then exposing it like an image. It can be performed by latent image forming means. The electrostatic latent image forming means includes, for example, a charging device (2) for charging the surface of the latent image carrier (1) and an exposure device (3) for exposing the surface of the latent image carrier (1) imagewise. At least.

The charging can be performed, for example, by applying a voltage to the surface of the latent image carrier (1) using the charging device (2).
The charging device (2) is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the charging device (2) includes a conductive or semiconductive roller, brush, film, rubber blade, etc. And non-contact chargers using corona discharge such as corotron and scorotron.

The shape of the charging device (2) may be a magnetic brush, a fur brush or the like in addition to the roller, and can be selected according to the specifications and form of the electrophotographic apparatus. In the case of using a magnetic brush, the magnetic brush is composed of, for example, various ferrite particles such as Zn-Cu ferrite as a charging member, and a non-magnetic conductive sleeve for supporting the same, and a magnet roll included therein. . In addition, when using a brush, for example, as a material of the fur brush, a fur treated with carbon, copper sulfide, metal or metal oxide is used, and this is wound around a metal or other conductive core. It is configured by pasting.
The charging device (2) is not limited to the contact type charger as described above, but an image forming apparatus in which ozone generated from the charger is reduced is obtained. Therefore, a contact type charger is used. It is preferable.

  The exposure can be performed, for example, by exposing the surface of the photoreceptor imagewise using the exposure apparatus (3). The exposure device (3) is not particularly limited as long as the surface of the latent image carrier (1) charged by the charging device (2) can be exposed like an image to be formed. For example, various exposure devices such as a copying optical system, a rod lens array system, a laser optical system, and a liquid crystal shutter optical system may be used.

  The development can be performed, for example, by developing the electrostatic latent image using the toner of the present invention, and can be performed by the developing device (4). The developing device (4) is not particularly limited as long as it can be developed using the toner of the present invention, for example, and can be appropriately selected from known ones. For example, the developing device (4) contains the toner of the present invention, Preferable examples include those having at least a developing unit that can apply toner to the electrostatic latent image in a contact or non-contact manner.

  The developing device (4) carries toner on its peripheral surface, rotates in contact with the latent image carrier (1), and supplies toner to the electrostatic latent image formed on the latent image carrier (1). The developing roller (40) that performs development and a thin layer forming member (41) that contacts the peripheral surface of the developing roller (40) and thins the toner on the developing roller (40) are preferable.

  As the developing roller (40), either a metal roller or an elastic roller is preferably used. There is no restriction | limiting in particular as a metal roller, Although it can select suitably according to the objective, For example, an aluminum roller etc. are mentioned. By performing a blasting process on the metal roller, it is possible to produce the developing roller (40) having an arbitrary surface friction coefficient relatively easily. Specifically, by treating the aluminum roller with glass bead blasting, the roller surface can be roughened, and an appropriate toner adhesion amount can be obtained on the developing roller.

As the elastic roller, a roller coated with an elastic rubber layer is used, and a surface coat layer made of a material that is easily charged to a polarity opposite to that of the toner is provided on the surface. The elastic rubber layer is set to a hardness of 60 degrees or less according to JIS-A in order to prevent toner deterioration due to pressure concentration at the contact portion with the thin layer forming member (41). The surface roughness (Ra) is set to 0.3 to 2.0 μm, and a necessary amount of toner is held on the surface. Further, since the developing roller (40) is applied with a developing bias for forming an electric field with the latent image carrier (1), the elastic rubber layer has a resistance value of 10 ³ to 10 ¹⁰ Ω. Is set. The developing roller (40) rotates in the clockwise direction, and conveys the toner held on the surface to a position facing the thin layer forming member (41) and the latent image carrier (1).

  The thin layer forming member (41) is provided at a position lower than the contact position between the supply roller (42) and the developing roller (40). The thin layer forming member (41) is made of a metal leaf spring material such as stainless steel (SUS) or phosphor bronze, and the free end is brought into contact with the surface of the developing roller (40) with a pressing force of 10 to 40 N / m. Therefore, the toner that has passed under the pressure is thinned and charged by frictional charging. Further, a regulating bias having a value offset in the same direction as the charging polarity of the toner with respect to the developing bias is applied to the thin layer forming member (41) in order to assist frictional charging.

There is no restriction | limiting in particular as a rubber elastic body which comprises the surface of a developing roller (40), Although it can select suitably according to the objective, For example, a styrene-butadiene-type copolymer rubber, an acrylonitrile-butadiene-type copolymer weight Examples include coalesced rubber, acrylic rubber, epichlorohydrin rubber, urethane rubber, silicone rubber, or a blend of two or more thereof. Among these, a blend rubber of epichlorohydrin rubber and acrylonitrile-butadiene copolymer rubber is particularly preferable.
The developing roller (40) is manufactured, for example, by covering the outer periphery of the conductive shaft with a rubber elastic body. The conductive shaft is made of a metal such as stainless steel (SUS), for example.

  The transfer can be performed, for example, by charging the latent image carrier (1), and can be performed by a transfer roller. The transfer roller includes a primary transfer unit that transfers a toner image onto an intermediate transfer member (6) to form a transfer image, and a secondary transfer unit (transfer) that transfers the transfer image onto a recording paper (P). An embodiment having a roller (8) is preferred. At this time, two or more colors, preferably full color toners are used as toners, and a primary transfer means for forming a composite transfer image by transferring the toner image onto the intermediate transfer member (6), and recording the composite transfer image An embodiment having secondary transfer means for transferring onto the paper (P) is more preferable.

The intermediate transfer member (6) is not particularly limited, and can be appropriately selected from known transfer members according to the purpose. For example, a transfer belt and the like are preferable.
The transfer means (primary transfer means, secondary transfer means) preferably has at least a transfer device that peels and charges the toner image formed on the latent image carrier (1) to the recording paper (P) side. . There may be one transfer means, or two or more transfer means. Examples of the transfer means include a corona transfer device using corona discharge, a transfer belt, a transfer roller, a pressure transfer roller, and an adhesive transfer device.

  The recording paper (P) is typically plain paper, but is not particularly limited as long as it can transfer an unfixed image after development, and can be appropriately selected according to the purpose. A PET base for OHP can also be used.

For example, the fixing can be performed on the toner image transferred to the recording paper (P) by using a fixing unit, and is performed each time the toner image of each color is transferred to the recording paper (P). Alternatively, it may be performed at the same time in a state where toner images of respective colors are laminated.
The fixing unit is not particularly limited and may be appropriately selected depending on the intended purpose. However, a known heating and pressing unit is preferable. Examples of the heating and pressing means include a combination of a heating roller and a pressure roller, a combination of a heating roller, a pressure roller, and an endless belt. The heating temperature by the heating and pressurizing means is preferably 80 to 200 ° C.

A soft roller type fixing device having a fluorine-based surface layer composition as shown in FIG. 2 may be used. This is because the heating roller (9) has an elastic body layer (11) made of silicone rubber and a PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) surface layer (12) on an aluminum core bar (10). The heater (13) is provided inside the aluminum cored bar. The pressure roller (14) has an elastic layer (16) made of silicone rubber and a PFA surface layer (17) on an aluminum cored bar (15). The recording paper (P) on which the unfixed image (18) is printed is passed as shown.
In the present invention, for example, a known optical fixing device may be used together with or instead of the fixing unit depending on the purpose.

  The neutralization can be performed, for example, by applying a neutralization bias to the latent image carrier, and can be suitably performed by a neutralization unit. The neutralizing means is not particularly limited as long as it can apply a neutralizing bias to the latent image carrier, and can be appropriately selected from known static eliminators. For example, a neutralizing lamp is preferable. It is done.

  Cleaning can be suitably performed, for example, by removing the toner remaining on the photoreceptor by a cleaning means. The cleaning means is not particularly limited and may be any one selected from known cleaners as long as it can remove the toner remaining on the photosensitive member. For example, a magnetic brush cleaner, an electrostatic brush cleaner, or a magnetic roller can be selected. A cleaner, a blade cleaner, a brush cleaner, a web cleaner and the like are preferable.

  The recycling can be suitably performed, for example, by transporting the toner removed by the cleaning unit to the developing unit by the recycling unit. There is no restriction | limiting in particular as a recycle means, A well-known conveyance means etc. are mentioned.

Control can be suitably performed by controlling each means by a control means, for example. The control means is not particularly limited as long as each means can be controlled, and can be appropriately selected according to the purpose. Examples thereof include devices such as a sequencer and a computer.
According to the image forming apparatus, the image forming method, and the process cartridge of the present invention, an excellent image can be obtained by using the electrostatic latent image developing toner that has excellent fixability and does not deteriorate due to stress in the developing process. Can be provided.

<Multicolor image forming apparatus>
FIG. 3 is a schematic diagram showing an example of a multicolor image forming apparatus to which the present invention is applied. FIG. 3 shows a tandem type full-color image forming apparatus.

  In FIG. 3, the image forming apparatus houses a latent image carrier (1) that is driven to rotate in the clockwise direction in FIG. 3 in a main body housing (not shown), and around the latent image carrier (1). A charging device (2), an exposure device (3), a developing device (4), an intermediate transfer member (6), a support roller (7), a transfer roller (8) and the like are arranged. Although not shown, the image forming apparatus includes a paper feeding cassette that stores a plurality of recording papers. The recording paper (P) in the paper feeding cassette is paired with a pair of registration rollers (not shown) by a paper feeding roller (not shown). After the timing adjustment, the sheet is fed between the intermediate transfer member (6) and the transfer roller (8) and fixed by the fixing means (19).

  The image forming apparatus rotates the latent image carrier (1) clockwise in FIG. 3, uniformly charges the latent image carrier (1) with the charging device (2), and then exposes the exposure device (3). The electrostatic image is formed on the latent image carrier (1) by irradiating the laser modulated with the image data, and the developing device (4) forms the latent image carrier (1) on which the electrostatic latent image is formed. Develop with toner attached. The image forming apparatus transfers the toner image formed by attaching the toner to the latent image carrier with the developing device (4) from the latent image carrier (1) to the intermediate transfer member. This is performed for each of the four colors of cyan (C), magenta (M), yellow (Y), and black (K) to form a full-color toner image.

  Next, FIG. 4 is a schematic view showing an example of a revolver type full-color image forming apparatus. In this image forming apparatus, a plurality of color toners are sequentially developed on one latent image carrier (1) by switching the operation of the developing device. Then, the color toner image on the intermediate transfer body (6) is transferred to the recording paper (P) by the transfer roller (8), the recording paper (P) to which the toner image is transferred is conveyed to the fixing unit, and the fixed image is transferred. obtain.

  On the other hand, the image forming apparatus further rotates the latent image carrier (1) on which the toner image is transferred to the recording paper (P) by the intermediate transfer member (6), and the latent image carrier (1) by the cleaning unit (5). ) The toner remaining on the surface is removed by scraping with a blade, and then the charge is removed by the charge removing unit. The image forming apparatus uniformly charges the latent image carrier (1) neutralized by the neutralization unit with the charging device (2), and then performs the next image formation as described above. The cleaning unit (5) is not limited to scraping off the residual toner on the latent image carrier (1) with a blade. For example, the cleaning unit (5) scrapes off the residual toner on the latent image carrier (1) with a fur brush. It may be a thing.

In the image forming method and the image forming apparatus of the present invention, since the toner of the present invention is used as the developer, a good image can be obtained.
<Process cartridge>
The process cartridge of the present invention can develop an electrostatic latent image carrier carrying an electrostatic latent image and the electrostatic latent image carried on the electrostatic latent image carrier using the toner of the present invention. A developing means for forming a visual image, and further comprising other means such as a charging means, a developing means, a transfer means, a cleaning means, and a static elimination means, which are appropriately selected as necessary. The image forming apparatus main body is detachable.

  The developing means includes a developer container that contains the toner or developer of the present invention, and a developer carrier that carries and transports the toner or developer contained in the developer container. And a layer thickness regulating member for regulating the thickness of the toner layer to be carried. The process cartridge of the present invention can be detachably provided in various electrophotographic apparatuses, facsimiles, and printers, and is preferably detachably provided in the image forming apparatus of the present invention described later.

  For example, as shown in FIG. 5, the process cartridge includes a latent image carrier (1), and includes a charging device (2), a developing device (4), a transfer roller (8), and a cleaning unit (5). In addition, other means are provided as necessary. In FIG. 5, (L) shows exposure from the exposure apparatus, and (P) shows recording paper. As the latent image carrier (1), the same one as the image forming apparatus can be used. An arbitrary charging member is used for the charging device (2).

Next, the image forming process using the process cartridge shown in the drawing will be described. The latent image carrier (1) is charged by the charging device (2) while being rotated in the direction of the arrow, and exposure by an exposure means (not shown) (not shown). L), an electrostatic latent image corresponding to the exposure image is formed on the surface. The electrostatic latent image is developed with toner by the developing device (4), and the toner development is transferred onto the recording paper (P) by the transfer roller (8) and printed out. Next, the surface of the latent image carrier after the image transfer is cleaned by the cleaning unit (5), further neutralized by a neutralizing unit (not shown), and the above operation is repeated again.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to these Examples.
Hereinafter, “parts” and “%” indicate parts by mass and mass% unless otherwise specified.

(Synthesis of polyester)
[Synthesis of Polyester 1]
229 parts of bisphenol A ethylene oxide 2-mole adduct, 400 parts of bisphenol A propylene oxide 2-mole adduct, 208 parts of terephthalic acid, 46 parts of adipic acid, and dibutyltin in a reaction vessel equipped with a condenser and a nitrogen inlet tube 2 parts of oxide were charged and reacted at 230 ° C. for 8 hours under normal pressure. Next, after reacting for 7 hours under a reduced pressure of 10 to 18 mmHg, 20 parts of trimellitic anhydride is added to the reaction vessel, and the reaction is performed under normal pressure at 180 ° C. until the softening point becomes 115 ° C., [Polyester 1] was synthesized.

[Synthesis of Polyester 2]
In a reaction vessel equipped with a cooling tube stirrer and a nitrogen introduction tube, 160 parts of bisphenol A ethylene oxide 2-mole adduct, 560 parts of bisphenol A propylene oxide 2-mole adduct, 230 parts of terephthalic acid, 20 parts of adipic acid and dibutyltin oxide 2 parts were charged and reacted at 230 ° C. for 8 hours under normal pressure. Next, after reacting for 7 hours under a reduced pressure of 1.3 to 2.0 kPa (10 to 15 mmHg), 20 parts of trimellitic anhydride is added to the reaction vessel, and the softening point is 170 ° C under normal pressure. [Polyester 2] was synthesized by reacting until it reached 93 ° C.

[Synthesis of polyester 3]
In a reaction vessel equipped with a cooling tube stirrer and a nitrogen introduction tube, 160 parts of bisphenol A ethylene oxide 2-mole adduct, 560 parts of bisphenol A propylene oxide 2-mole adduct, 230 parts of terephthalic acid, 20 parts of adipic acid and dibutyltin oxide 2 parts were charged and reacted at 230 ° C. for 8 hours under normal pressure. Next, after reacting for 7 hours under a reduced pressure of 1.3 to 2.0 kPa (10 to 15 mmHg), 20 parts of trimellitic anhydride is added to the reaction vessel, and the softening point is 170 ° C under normal pressure. [Polyester 3] was synthesized by reacting until the temperature reached 89 ° C.

[Synthesis of Polyester 4]
229 parts of bisphenol A ethylene oxide 2-mole adduct, 400 parts of bisphenol A propylene oxide 2-mole adduct, 208 parts of terephthalic acid, 46 parts of adipic acid, and dibutyltin in a reaction vessel equipped with a condenser and a nitrogen inlet tube 2 parts of oxide were charged and reacted at 230 ° C. for 8 hours under normal pressure. Next, after reacting under reduced pressure of 10 to 18 mmHg for 7 hours, 20 parts of trimellitic anhydride is added to the reaction vessel, and the reaction is carried out at 180 ° C under normal pressure until the softening point is 122 ° C. [Polyester 4] was synthesized.

(Manufacture of resin fine particles)
[Production of resin fine particle dispersion 1]
In a 5 liter stainless steel kettle, 1500 g of [Polyester 1], 100 g of anionic surfactant “Neopelex G-15 (manufactured by Kao)” [Sodium dodecylbenzenesulfonate (solid content: 15% by weight)], nonionic Surfactant “Emulgen 430 (manufactured by Kao Corporation)” [Polyoxyethylene (26 mol) oleyl ether (HLB: 16.2)] 15 g and 5 wt% potassium hydroxide aqueous solution 689 g were mixed with a chi-type stirrer at 200 r / min. The mixture was dispersed at 25 ° C. with stirring. The contents were stabilized at 95 degrees and held for 2 hours under stirring at 200 r / min with a chi-type stirrer. Subsequently, deionized water was added dropwise at a rate of 15 g / min to a solid content concentration of 25% under a stirring rate of 200 r / min with a chi-type stirrer to obtain [resin fine particle dispersion 1].
The obtained [resin fine particle dispersion liquid 1] had a volume average particle diameter (D50) of 125 nm.

[Production of resin fine particle dispersion 2]
[Resin fine particle dispersion 2] was obtained in the same manner as [Resin fine particle dispersion 1] except that 1500 g of [Polyester 2] was used instead of 1500 g of [Polyester 1]. The obtained [resin fine particle dispersion liquid 2] had a volume average particle diameter (D50) of 140 nm.

[Production of resin fine particle dispersion 3]
[Resin fine particle dispersion 3] was obtained in the same manner as [Resin fine particle dispersion 1] except that 1500 g of [Polyester 3] was used instead of 1500 g of [Polyester 1]. The obtained [resin fine particle dispersion liquid 3] had a volume average particle diameter (D50) of 127 nm.

[Production of resin fine particle dispersion 4]
[Resin fine particle dispersion 4] was obtained in the same manner as [Resin fine particle dispersion 1] except that 1500 g of [Polyester 4] was used instead of 1500 g of [Polyester 1]. The obtained [resin fine particle dispersion 4] had a volume average particle diameter (D50) of 130 nm.

[Production of resin fine particle dispersion 5]
In a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube, 0.7 part of sodium dodecyl sulfate and 500 parts of ion-exchanged water are dissolved by heating to 80 ° C. with stirring, and then potassium persulfate. A solution of 2.6 parts dissolved in 100 parts of ion-exchanged water was added, and 15 minutes later, 185 parts of styrene monomer, 15 parts of butyl acrylate, 60 parts of methyl methacrylate, and 4.2 parts of n-octanethiol The mixed solution was added dropwise over 90 minutes, and then the polymerization reaction was further maintained at 80 ° C. for 60 minutes. Then, it was cooled and ion-exchanged water was added so that the solid content concentration was 25%, and [resin fine particle dispersion 5] was obtained. The particle size of the resin fine particles was 110 nm.

[Production of resin fine particle dispersion 6]
In a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube, 0.7 part of sodium dodecyl sulfate and 500 parts of ion-exchanged water are dissolved by heating to 80 ° C. with stirring, and then potassium persulfate. A solution prepared by dissolving 2.6 parts in 100 parts of ion-exchanged water was added, and 15 minutes later, 185 parts of styrene monomer, 15 parts of butyl acrylate, 60 parts of methyl methacrylate, 60 parts of methoxydiethylene glycol methacrylate n-octanethiol 4 2 parts of the monomer mixture was added dropwise over 90 minutes, and then the polymerization reaction was continued at 80 ° C. for an additional 60 minutes. Thereafter, the mixture was cooled and ion-exchanged water was added so that the solid content concentration was 25% to obtain [resin fine particle dispersion 6]. The particle size of the resin fine particles was 115 nm.

[Production of resin fine particle dispersion 7]
In a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introducing tube, 1.2 parts of sodium dodecyl sulfate and 500 parts of ion-exchanged water are dissolved by heating to 80 ° C. with stirring, and then potassium persulfate. A solution of 2.6 parts dissolved in 100 parts of ion-exchanged water was added, and 15 minutes later, 185 parts of styrene monomer, 15 parts of butyl acrylate, 60 parts of methyl methacrylate, and 4.2 parts of n-octanethiol The mixed solution was added dropwise over 90 minutes, and then the polymerization reaction was further maintained at 80 ° C. for 60 minutes. Thereafter, it was cooled and ion-exchanged water was added so that the solid content concentration was 25% to obtain [resin fine particle dispersion 7]. The particle diameter of the resin fine particles was 60 nm.

[Manufacture of master batch 1]
C. I. Pigment Red 122: 40 parts, [Polyester 1]: 60 parts, and Water: 30 parts were mixed with a Henschel mixer to obtain a mixture in which water was soaked into the pigment aggregate.
This was kneaded for 45 minutes with two rolls set at a roll surface temperature of 130 ° C. and pulverized to a size of 1 mm with a pulverizer to obtain [Masterbatch 1].

(Preparation of aqueous phase)
970 parts of ion-exchanged water, 60 parts of a 25 wt% aqueous dispersion of organic resin fine particles (styrene-methacrylic acid-butyl acrylate-methacrylic acid ethylene oxide adduct sulfate sodium salt copolymer) for dispersion stabilization, dodecyl diphenyl ether When 180 parts of a 48.5% aqueous solution of sodium disulfonate and 100 parts of ethyl acetate were mixed and stirred, the pH reached 6.2. A 10% aqueous sodium hydroxide solution was added dropwise thereto to adjust the pH to 9.5 to obtain [Aqueous Phase 1].

(WAX dispersion preparation process)
In a container equipped with a stirring bar and a thermometer, 24 parts of [Polyester 1], 12 parts of [paraffin wax (melting point: 72 ° C.)], 100 parts of ethyl acetate, styrene / polyethylene polymer (Tg = 72 ° C., Charge 6 parts of number average molecular weight 7100), heat up to 80 ° C. with stirring, hold at 80 ° C. for 5 hours, cool to 30 ° C. in 1 hour, and use bead mill (Ultra Visco Mill, manufactured by IMEX) Then, WAX dispersion was carried out under the conditions of a liquid feeding speed of 1 kg / hr, a disk peripheral speed of 6 m / sec, 80% by volume of 0.5 mm zirconia beads, and 3 passes to obtain [WAX Dispersion 1].

(Oil phase preparation process)
After mixing 100 parts of [Polyester 1], 15 parts of [Masterbatch 1], 30 parts of [WAX Dispersion 1] and 80 parts of ethyl acetate at 8,000 rpm with a TK homomixer (manufactured by Tokushu Kika), 15 parts of [Prepolymer 1] was added and mixed with TK homomixer at 8,000 rpm for 2 minutes to obtain [Oil Phase 1]. It was 58 mass% when solid content of the obtained [oil phase 1] was measured.

(Core particle creation process)
[Oil phase 1] 100 parts of [aqueous phase 1] 100 parts, and in order to suppress the temperature rise due to the shear heat of the mixer, cooling in a water bath so that the temperature in the liquid is in the range of 20-23 ℃ While adjusting, adjust the rotation speed at 8,000-15,000 rpm using a TK homomixer and mix for 2 minutes, then stir for 10 minutes while adjusting the rotation speed between 130-350 rpm with a three-one motor with an anchor blade attached Thus, [core particle slurry 1] was obtained in which oil phase droplets serving as core particles were dispersed in an aqueous phase.

(Shelling process)
While stirring [Core Particle Slurry 1] at a rotation speed of 350 rpm with a three-one motor equipped with anchor blades, 5.3 parts of [Resin Fine Particle Dispersion 1] is applied for 1 minute while the liquid temperature is 22 ° C. After forming the first shell layer, the number of revolutions was adjusted to 450 rpm, and 10.6 parts of [resin fine particle dispersion 5] and 15.9 parts of ion-exchanged water were mixed for 3 minutes. It was dripped. Stirring was continued for 30 minutes to obtain [Composite Particle Slurry 1].

(Demelting process)
[Composite particle slurry 1] was put into a container equipped with a stirrer and a thermometer, and the solvent was removed at 30 ° C. for 8 hours while stirring to obtain [Dispersion slurry 1].

(Washing / drying process)
[Dispersion Slurry 1] After filtering 100 parts under reduced pressure,
(1): 100 parts of ion-exchanged water was added to the filter cake, mixed with a TK homomixer (10 minutes at 12,000 rpm), and then filtered.
(2): 900 parts of ion-exchanged water was added to the filter cake of (1), ultrasonic vibration was applied, and the mixture was mixed with a TK homomixer (30 minutes at 12,000 rpm), and then filtered under reduced pressure. This operation was repeated so that the electric conductivity of the reslurry liquid was 10 μC / cm or less.
(3): 10% hydrochloric acid was added so that the reslurry liquid of (2) had a pH of 4, and the mixture was filtered as it was with a three-one motor for 30 minutes.
(4): 100 parts of ion-exchanged water was added to the filter cake of (3), mixed with a TK homomixer (10 minutes at 12,000 rpm) and then filtered. This operation was repeated so that the reslurry liquid had an electric conductivity of 10 μC / cm or less to obtain [Filter Cake 1].
[Filtration cake 1] was dried at 45 ° C. for 48 hours in a circulating drier, and sieved with a mesh of 75 μm to obtain [Toner 1].

[Toner 2] was obtained in the same manner as in Example 1 except that the shelling step was changed as follows. (Shelling process)
While stirring [core particle slurry 1] with a three-one motor with an anchor blade adjusted to a rotation speed of 350 rpm, 5.3 parts of [resin fine particle dispersion 2] is applied for 1 minute while the liquid temperature is 22 ° C. Then, the rotational speed was adjusted to 450 rpm, and 17.0 parts of [resin fine particle dispersion 5] and 25.4 parts of ion-exchanged water were added dropwise over 3 minutes. Stirring was continued for 30 minutes to obtain [Composite Particle Slurry 2].

[Toner 3] was obtained in the same manner as in Example 1 except that the shelling step was changed as follows.
(Shelling process)
While stirring [Core Particle Slurry 1] at a rotation speed of 350 rpm with a three-one motor equipped with anchor blades, 5.3 parts of [Resin Fine Particle Dispersion 1] is applied for 1 minute while the liquid temperature is 22 ° C. Then, the number of revolutions was adjusted to 450 rpm, and 6.4 parts of [resin fine particle dispersion 5] and 9.5 parts of ion-exchanged water were added dropwise over 3 minutes. Stirring was continued for 30 minutes to obtain [Composite Particle Slurry 3].

[Toner 4] was obtained in the same manner as in Example 1 except that the shelling step was changed as follows.
(Shelling process)
While stirring [Core Particle Slurry 1] at a rotation speed of 350 rpm with a three-one motor equipped with anchor blades, 5.3 parts of [Resin Fine Particle Dispersion 1] is applied for 1 minute while the liquid temperature is 22 ° C. Then, the number of revolutions was adjusted to 450 rpm, and 18.0 parts of [resin fine particle dispersion 5] and 27.0 parts of ion-exchanged water were added dropwise over 3 minutes. Stirring was continued for 30 minutes to obtain [Composite Particle Slurry 4].

[Toner 5] was obtained in the same manner as in Example 1 except that the shelling step was changed as follows.
(Shelling process)
While stirring [Core Particle Slurry 1] at a rotation speed of 350 rpm with a three-one motor equipped with anchor blades, 5.3 parts of [Resin Fine Particle Dispersion 1] is applied for 1 minute while the liquid temperature is 22 ° C. Then, the number of revolutions was adjusted to 450 rpm, and 7.4 parts of [resin fine particle dispersion 7] and 11.1 parts of ion-exchanged water were added dropwise over 3 minutes. Stirring was continued for 30 minutes to obtain [Composite Particle Slurry 5].

[Toner 6] was obtained in the same manner as in Example 1 except that the shelling step was changed as follows.
(Shelling process)
While stirring [Core Particle Slurry 1] at a rotation speed of 350 rpm with a three-one motor equipped with anchor blades, 5.3 parts of [Resin Fine Particle Dispersion 1] is applied for 1 minute while the liquid temperature is 22 ° C. Then, the number of revolutions was adjusted to 450 rpm, and 15.9 parts of [resin fine particle dispersion 6] and 23.9 parts of ion-exchanged water were added dropwise over 3 minutes. Stirring was continued for 30 minutes to obtain [Composite Particle Slurry 6].

(Comparative Example 1)
[Toner 7] was obtained in the same manner as in Example 1 except that the shelling step was changed as follows.
(Shelling process)
While stirring [Core Particle Slurry 1] with a three-one motor with anchor blades adjusted to a rotational speed of 350 rpm, 5.3 parts of [Resin Fine Particle Dispersion 4] is applied for 1 minute while the liquid temperature is 22 ° C. Then, the number of revolutions was adjusted to 450 rpm, and 10.6 parts of [resin fine particle dispersion 5] and 15.9 parts of ion-exchanged water were added dropwise over 3 minutes. Stirring was continued for 30 minutes to obtain [Composite Particle Slurry 7].

(Comparative Example 2)
[Toner 8] was obtained in the same manner as in Example 1 except that the shelling step was changed as follows.
(Shelling process)
While stirring [core particle slurry 1] at a rotation speed of 350 rpm with a three-one motor equipped with anchor blades, 5.3 parts of [resin fine particle dispersion 3] is applied for 1 minute while the liquid temperature is 22 ° C. Then, the number of revolutions was adjusted to 450 rpm, and 10.6 parts of [resin fine particle dispersion 5] and 15.9 parts of ion-exchanged water were added dropwise over 3 minutes. Stirring was continued for 30 minutes to obtain [Composite Particle Slurry 8].

(Comparative Example 3)
[Toner 9] was obtained in the same manner as in Example 1 except that the shelling step was changed as follows.
(Shelling process)
While the [core particle slurry 1] is stirred at a rotational speed of 450 rpm with a three-one motor equipped with anchor blades, 10.6 parts of [resin fine particle dispersion 5] and ion-exchanged water 15 at a liquid temperature of 22 ° C. A mixture of 9 parts was added dropwise over 3 minutes. Stirring was continued for 30 minutes to obtain [Composite Particle Slurry 9].

(Comparative Example 4)
[Toner 10] was obtained in the same manner as in Example 1 except that the shelling step was changed as follows.
(Shelling process)
While stirring [Core Particle Slurry 1] at a rotation speed of 350 rpm with a three-one motor equipped with anchor blades, 5.3 parts of [Resin Fine Particle Dispersion 1] is applied for 1 minute while the liquid temperature is 22 ° C. Then, the number of revolutions was adjusted to 450 rpm and stirring was continued for 30 minutes to obtain [Composite Particle Slurry 10].

(Comparative Example 5)
[Toner 11] was obtained in the same manner as in Example 1 except that the shelling was not performed.

(Comparative Example 6)
[Toner 12] was obtained in the same manner as in Example 1 except that the shelling step was changed as follows.
(Shelling process)
While stirring [core particle slurry 1] with a three-one motor with an anchor blade adjusted to a rotation speed of 350 rpm, 5.3 parts of [resin fine particle dispersion 2] is applied for 1 minute while the liquid temperature is 22 ° C. Then, the number of revolutions was adjusted to 450 rpm, and 10.6 parts of [resin fine particle dispersion 1] and 15.9 parts of ion-exchanged water were added dropwise over 3 minutes. Stirring was continued for 30 minutes to obtain [Composite Particle Slurry 12].

The toners 1 to 12 were evaluated by the following methods. The physical properties of the toner are shown in Table 1, and the evaluation results are shown in Table 2.
Although used as a one-component developer, the toner of the present invention may be externally added or used as a two-component developer together with a carrier.

<Evaluation method>
(Second shell coverage)
The toner is observed with a scanning electron microscope (SEM), and the coverage of the second shell covering the first shell layer is determined from the obtained SEM image.
Hereinafter, the calculation method will be described.
From the surface area of the toner particles measured by the image analysis type particle size distribution measurement software [Mac-View] (manufactured by Mountec Co., Ltd.) and the area of the protrusions (resin fine particles) on the surface of the toner particles measured in the same manner, the surface area of the toner particles The coverage of the protrusions was calculated. Regarding the coverage, the coverage was calculated by the above method for 100 or more toner particles, and the average value was used as the evaluation value.
In Comparative Example 3 and Comparative Example 6, measurement was not possible because the resin particles were completely buried and there were no protrusions.

(Second shell diameter)
The toner particles are observed with a scanning electron microscope (SEM), and the average diameter of the second shell is obtained from the obtained SEM image.
Hereinafter, a method for calculating the average diameter of the second shell will be described.
The equivalent circle diameter was calculated from the sum of the number of protrusions on the toner particle surface and the area of the protrusions measured by image analysis type particle size distribution measurement software [Mac-View] (manufactured by Mountec Co., Ltd.). The equivalent circle diameter was calculated by the above method for 100 or more toner particles, and the average value was taken as the diameter of the second shell.
In Comparative Example 3 and Comparative Example 6, measurement was not possible because the resin particles were completely buried and there were no protrusions.

(Particle size of resin fine particles)
It measured in the state of a dispersion liquid using LA-920 (Horiba Seisakusho).

(Softening point)
Using a flow tester (CFT-500 / manufactured by Shimadzu Corporation), 1.5 g of a measurement sample is weighed, and using a die of H1.0 mm × Φ1.0 mm, the heating rate is 3.0 ° C./min, the preheating time is 180 seconds. The measurement was performed under the conditions of a load of 30 kg and a measurement temperature range of 30 to 160 ° C., and the temperature at which the sample flowed out 1/2 was taken as the softening point of the toner.

(Fixing limit)
Toner was put in a modified IPSiO SP C220, and 19 sheets of 50 mm square unfixed solid images were printed on a Ricoh type 6200Y eye paper so that the adhesion amount was 10 g / m 2.
Next, using the modified fixing unit, the system speed was set to 280 mm / sec, and the prepared unfixed solid image was passed through to fix the image. The fixing temperature was tested from 120 ° C to 200 ° C in 5 ° C increments. The fixed image was folded inward, spread again, and then lightly rubbed with an eraser. The lowest temperature at which the crease did not disappear was defined as the minimum fixing temperature.
〔Evaluation criteria〕
○: Fixing lower limit temperature is less than 140 ° C
Δ: The minimum fixing temperature is 140 ° C. or higher and lower than 150 ° C.
×: The minimum fixing temperature is 150 ° C. or higher.

(Chargeability)
A predetermined print pattern with a B / W ratio of 6% was continuously printed on the toner (developer) in an N / N environment (23 ° C., 45%). After printing 50 sheets and 2000 sheets in a N / N environment (after endurance), the toner on the developing roller during blank paper pattern printing is sucked with a suction type small charge measuring device MODEL 210HS manufactured by Trek Japan Co., Ltd. The amount of charge was measured, and the charge amount after 50 sheets and 2000 sheets was evaluated. ○: The absolute value of the charge amount difference was less than 10 μC / g. Δ: The absolute value of the charge amount difference was not less than 10 μC / g and less than 15 μC / g. The absolute value of the charge amount difference is 15μC / g or more

JP 2009-53501 A Japanese Patent Laying-Open No. 2005-099233

DESCRIPTION OF SYMBOLS 1 Latent image carrier 2 Charging apparatus 3 Exposure apparatus 4 Developing apparatus 40 Developing roller 41 Thin layer forming member 42 Supply roller 5 Cleaning part 6 Intermediate transfer body 7 Support roller 8 Transfer roller 9 Heating roller 10 Aluminum core 11 Elastic body layer 12 PFA surface layer 13 Heater 14 Pressure roller 15 Aluminum core 16 Elastic layer 17 PFA surface layer 18 Unfixed image 19 Fixing means L Exposure P Recording paper T Electrostatic charge image developing toner

Claims (11)

  An electrophotographic toner granulated in an aqueous medium, wherein the toner has a core-shell structure, the core includes a colorant and a binder resin, and the shell covers the entire core surface. And a second shell made of resin fine particles fixed to the surface of the first shell, and the resin constituting the first shell has a softening point of 90 ° C. or higher and 120 ° C. or lower, An electrophotographic toner, wherein the resin constituting the shell is a vinyl resin. The electrophotographic toner according to claim 1, wherein the coverage of the first shell with the second shell is 30% or more and 80% or less. The toner according to claim 1, wherein an average diameter of an exposed portion of the vinyl resin particles of the second shell is 150 nm or more and 400 nm or less. The electrophotographic toner according to claim 1, wherein the vinyl resin fine particles contain 80% by mass or more of a portion derived from an aromatic compound having a vinyl polymerizable functional group. The electrophotographic toner according to claim 1, wherein the binder resin of the core is a polyester resin. The electrophotographic toner according to claim 1, wherein the resin constituting the first shell is a polyester resin. 7. The electrophotographic toner according to claim 1, wherein the toner is a magenta toner or a yellow toner. A developer comprising the electrophotographic toner according to claim 1. A process cartridge which integrally supports a latent image carrier, a developing means, a charging means and / or a cleaning means, and is detachable from the main body of the image forming apparatus, wherein the developing means is claimed. 9. A process cartridge which holds the developer according to item 8. A charging step for uniformly charging the surface of the latent image carrier;
An exposure process for exposing the surface of the charged latent image carrier based on the image data and writing an electrostatic latent image;
A developer layer having a predetermined layer thickness is formed on the developer carrier by a developer layer regulating member, and the electrostatic latent image formed on the surface of the latent image carrier is developed through the developer layer to be visualized. A development process to
A transfer step of transferring a visible image on the surface of the latent image carrier to the transfer target;
A fixing step of fixing a visible image on the transfer target,
An image forming method using the developer according to claim 8 as the developer. A latent image carrier for carrying a latent image, a charging means for uniformly charging the surface of the latent image carrier, and exposing the charged surface of the latent image carrier based on image data to write an electrostatic latent image An exposure unit; a developing unit that supplies toner to the electrostatic latent image formed on the surface of the latent image carrier to make it visible; and a transfer unit that transfers the visible image on the surface of the latent image carrier to the transfer target; An image forming apparatus comprising: a fixing unit that fixes a visible image on a transfer target, wherein the developing unit holds the developer according to claim 8.

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